Service

What are brake calipers and how do they work?

The brake caliper used in disc brake systems is a cast metal housing that contains one or more pistons. When you push on the brake pedal, you create hydraulic pressure in the master cylinder that forces the piston in the caliper outward against the brake pads, and applies force to the brake pads. The brake pads then clamp tightly onto the brake rotor, slowing your car.

When to replace a brake caliper:

Sticking or Seized Components. If the caliper piston, bushings, or slide pins are binding or seized, it can result in either continued contact of the brake pads with the rotor, causing it to overheat — sometimes getting so hot you will detect a burning odor. Or, it can inhibit braking of that caliper, causing the vehicle to pull to one side when braking.

Fluid leaks from piston seal in the caliper. If the caliper leaks at the piston, or even bleeder screw, it must be removed from the vehicle for rebuilding or replacement.

How do mechanics replace a brake caliper?

Most cars have floating calipers and thus the replacement procedure will be as follows:

Raise and safely support vehicle with jack stands. Remove wheel and tire assembly.

Relieve any residual brake system pressure by opening the caliper bleeder screw.

Detach flexible rubber hose to the caliper while capturing the brake fluid that will leak out. Discard copper sealing washers for the hose fitting.

Remove bolts holding caliper to the torque plate. Remove caliper.

To install the new caliper the above steps are reversed. New copper sealing washers are used and a calibrated torque wrench is used to tighten the hose connection to the caliper, the mounting bolt(s) and the wheel lug nuts.

Finally, the brake system is bled to remove all air and the vehicle is road tested to confirm normal operation of the brakes.

Is it safe to drive with a brake caliper problem?

No. Should a sticking brake caliper cause severe pulling of the vehicle to one side, perhaps even with the brakes not applied, have the vehicle inspected and repaired as soon as possible. If a sticking caliper is causing extreme heat at a wheel position, that can cause overheating of the wheel bearing grease, which is in very close proximity to the caliper and brake rotor. This might cause wheel bearing failure earlier than normal.

When replacing a brake caliper keep in mind:

Whenever major repairs are performed on a vehicle’s brake system, the entire brake system should be at least visually inspected.

If a caliper on one side of an axle is sticking, best practice is to replace both calipers on the axle.

If a caliper is replaced, generally the brake pads (on both ends of the axle) must be replaced and the rotors either resurfaced or replaced. If a caliper is faulty, replacing the caliper alone will generally yield suboptimal results.

The torque plate to which the caliper is bolted should be inspected for excessive corrosion and cleaned as necessary, otherwise the new brake pads could stick on that component even after the caliper has been replaced.